The present invention relates to magnetic materials, and more particularly relates to magnetic nanocomposite materials including iron, rare earth elements, boron, refractory metals and cobalt which have favorable magnetic properties and are suitable for making bonded magnets.
Magnetic alloys containing neodymium, iron and boron have been widely studied for use in sintered and bonded magnets due to their favorable magnetic properties. The Nd2Fe14B phase has been identified as a hard magnetic phase exhibiting particularly good magnetic properties.
U.S. Pat. Nos. 4,402,770, 4,409,043 and Re. U.S. Pat. No. 34,322 to Koon, which are incorporated herein by reference, disclose magnetic alloys comprising lanthanum and other rare earth elements, transition metals such as iron and cobalt, and boron within specified ranges. Although the disclosed alloys have been found to possess good magnetic properties, such alloys do not have optimal properties, and have not become commercially viable.
The present invention provides favorable magnetic properties and are suitable for commercial production of bonded magnets.
The present invention provides a nanocomposite magnetic material of controlled composition which exhibits improved magnetic properties and can be easily processed. An object of the present invention is to provide a nanocomposite magnetic material comprising Fe, rare earth elements (preferably La, Pr and Nd), B, refractory metals and Co within specified ranges.
Compositions of the present invention can be of the formula: (Nd1xe2x88x92yLay)vFe100xe2x88x92vxe2x88x92wxe2x88x92xxe2x88x92zCowMzBx, where M is at least one refractory metal selected from Ti, Zr, Hf, V, Nb, Ta, Cr, Mo and W; v is from about 5 to about 15; w is greater than or equal to 5; x is from about 9 to about 30; y is from about 0.05 to about 0.5; and z is from about 0.1 to about 5. Preferably, M is Cr.
A further object of the present invention is to provide a nanocomposite magnetic material including a hard magnetic phase, a soft magnetic phase, and, preferably a refractory metal boride precipitated phase. The hard magnetic phase is preferably Nd2Fe14B, while the soft magnetic phase preferably comprises xcex1-Fe, Fe3B or a combination thereof. Most preferably, the material comprises the xcex1-(Fe,Co) and R2(Fe, Co)14B phases.
The present invention provides a method of making a nanocomposite magnetic material. The method includes the steps of providing a molten composition comprising Fe, rare earth elements (preferably Nd and La), B, at least one refractory metal (preferably Cr), and Co, rapidly solidifying the composition to form a substantially amorphous material, and thermally treating the material.